Production of spray metal negatives of models



M. STC5$SEL Aug. 18, 1942.

PRODUCTION OF SPRAY METAL NEGATIVES OF MODELS Original Filed May 22. 1939 IN VEN TOR Max 5/5556] @404 49W ATTORNEY Patented Aug. 18, 1942 PRODUCTION OF SPRAY METAL NEG A'I'IVES OF'HODELS Max Stiissel, New York, N. Y., assignor to Otto Stosoel, Chicago,

Original application May 22, 1939, Serial No. 274,951. Divided and this app cation May 29, 1940, Serial No. 337,788. In Great Britain Jannary 11,1938

6 Claims. (01. 22-200) This invention relates to the production of spray metal negatives of models andparticularly the production of molds, dies, patterns, or the like, of the type that are particularly useful in the casting or molding of plastics such as synthetic resins rubber, Celluloid or glass and the like.

At the present, molds for this use are generally produced by cutting the molds from solid metal blocks by means of machining and engraving tools. This method involves considerable time and expense and is not commercially practicable for low-cost production, except when the molds thus made are used in mass production, where the cost of the mold can be distributed over numerous products made therefrom. Even then the length of time necessary to produce a mold is a material drawback.

A few attempts have been made to produce molds for this work by spraying metal upon a model or a positive and thus forming a mold or negative. Such attempts were unsuccessful because of distortion and inaccuracy and the tend ency of the sprayed metal to peel off the model,

particularly when spraying with metals having 25 a fusion point above 600 C. This tendency to peel is apparently due to uneven thermal stresses produced in the metal when it is sprayed upon the model and is particularly prevalent when the metal is sprayed to a thickness exceeding spray metal negative or mold formed on a model; and

Fig. 2 is a cross-sectional side elevation of a two-part divided or separable mold.

In carrying out my invention, the model or master pattern of the article to be reproduced and for which a mold is to be made, as for instance, a model or pattern of iron, steel, or other suitable material, is first provided with a thin coat of a relatively low melting point metal such as tin, zinc or cadmium. The negative or mold is obtained on the coating by spraying a higher melting point metal thereonto. The coating may be applied by hot dipping or, preferably, by electroplating and not only aids in the adherence of the metal of the negative or mold to the metal of the model but also facilitates separation of the two after the negative or mold is completed. The spray metal coating constitut ing the negative or mold of metal can be readily separated from the model by heating the two to the melting point of the coating (of lower melting point) to break the bond between the model and the negative or mold. Thus, a substantially accurate negative of the original is obtained.

The material of which the sprayed mold is to be made may be selected according to the conditions to which it is to be subjected or the use to which it is to be put. For example, aluminum or aluminum alloys, bronze or similar metals may be used if little strain is to be put on the mold or if the number of articles to be made therefrom is small. If, on the other hand, the mold is to be used for mass production, or if for any other reason it must be of harder material, such metals as steel, nickel, or chromenickel alloys, or the like may be used.

As a practical example, the negative or mold impossible to spray the model with a metal of may be made for instance in the following suflicient high fusion point and corresponding hardness to provide a usable negative or mold.

It is the purpose of my present invention to produce an accurate and usable negative or mold economically and commercially by spraying a model, either the original or a reproduced model, in such a manneras to overcome the heretofore mentioned difficulties, as well as other defects and limitations.

Further objects and their resultant advantages will be apparent from the following description taken in connection with the following drawing in which:

manner:

The model 20 (Fig. 1), preferably of metal, is, for example, clamped in and supported by a steel frame support 6, in order to avoid possible 5 distortion of the model while the metal of the drawing, and held therein by an upper clamping plate or frame I21; and screws l3, the clamping plate or frame 12a having if desired a sloping edge Ma and being preferably of proper size to retain the model 20 within the frame support 6. The lower side of the model, when placed in Fig. 1 is a cross-sectional side elevation of a the frame support 6, is preferably also supported by a metal I8 or sand, or some other suitable material, "held in position by the frame support and bottom plate l'l. Assuming the model 20 has been prepared by electro-plating a coating 24 01 low melting point metal thereon, it is then sprayed with successive layers 26 of suitable higher melting point metal until a spray metal coating of the desired thickness has been produced. While spraying the coated model, the same being preferably clamped in a suitable frame, thelayers 2B of sprayed metal will build 'up under the inclined edge Ila of frame I211.

small consumption, in which case it was here:

tofore economically impossible to do this because of the expense in producing a mold.

This application is a division of my co-pending application Serial No. 274,951, filed May 22, 1939. It will be apparent to those skilled in the art that minor variations and deviations from the required to prevent distortion of the model or matrix while the metal of the negative or mold is being sprayed thereon, it may be desirable to cool the model while the metal of the negative or mold is being so sprayed. This can be accomplished readily by circulating a cooling medium through the lower portion of the frame support '6.

In certain classes of molding, both surfaces of the molded article must be finished. In such cases, a two-part mold must be employed. In Fig. 2 there is illustrated a two-part mold of this character, both parts of the mold being made in accordance with the process outlined above. Such a mold is particularly adaptable to the manufacture of articles of synthetic resins and comprises two parts 3| and 32, both madeby the spraying of high melting point metals upon a model, aspreviously outlined. Each of the portions of the mold is preferably supported in frames 33 and 34, respectively, which are backed with suitable material to give the necessary rigidity to the two sections of the mold. The two portions of the mold are provided with studs 3'! and guides 38, respectively, to cause proper approach of the two sections of the mold when they are brought together.

The spray metal negative or mold, made in accordance with my invention, may be used either for the production ofanother model or the reproduction of articles like the first model.

It will be obvious to those skilled in the art that molds may be produced in accordance with the foregoing much quicker than the usual weeks of time now required and at a cost materially less than heretofore. Accurate molds may be produced in accordance with the invention at a low cost, which molds are wholly satisfactory and adequate for the reproduction of molded articles, even ii such articles are desired for samples or foregoing processes as described may be indulged in without departing from the spirit and scope of this invention, as defined in the appended claims.

I claim:

1. The method of producing a, negative of a model which comprises the steps of coating the model with a thin layer of at least one metal of low melting point, spraying metal of relatively higher melting point over said coated model until a substantial thickness has been reached, heating said layer to its melting point, and separating the model and spray metal negative.

2. The method of producing a negative of a model at least the surface of which is metal which comprises the steps of coating such'model with a thin layer of at least one metal of a melting point relatively lower than the melting point of the metal of the surface of said model, spraying metal of a melting point relatively higher than the melting point of said coatingmetal over said coated model until a substantial thickness has been reached, heating said layer to its melting point, and separating the model and spray metal negative.

3. Method in accordance with claim 2 in which said coating metal is at least one member selected from the group consisting of zinc, tin and cadmium.

4. Method in accordance with c1aim2 in which spraying metal of a melting point relatively higher than the melting points of said coating metal and said filling metal over said coated model until a substantial thickness has been reached, heating said layer and said filling to effect their melting and separating the model and spray metal negative.

6. Process of making negatives'in-metal of a matrix by metal spraying, which comprises applying to a matrix a substantially thin coat of a first metal, spraying the coated matrix with a second metal, said second metal having a melting point higher than the melting point of said first metal, to form a substantially coherent coating of said applied spray metal, melting said coat of said first metal and removing said spray metal coating substantially intact from 'said matrix.

MAX s'rossEL. 

